Metalization of flexible polymer sheets

ABSTRACT

A conductive grid formation system, apparatus, and related methods may include a drum having a conductive surface, an insulation layer coating said surface, and a grid pattern formed in the insulation layer to expose portions of the conductive surface. The drum surface may be rotated into and out of a chemical bath, such that a metallic grid is electrodeposited in the exposed portions of the conductive surface. A polymer sheet may be laminated to the surface of the drum and then removed, such that the metallic grid attaches to the polymer sheet and is removed with the polymer sheet. Heat, pressure, and/or adhesive may be utilized in various steps of the process, to facilitate preferential adhesion of the metallic grid to the polymer sheet.

CROSS-REFERENCES

The following related applications and materials are incorporatedherein, in their entireties, for all purposes: U.S. Pat. No. 8,993,364and U.S. Publication No.

2013/0269748 A1.

FIELD

This disclosure relates to systems and methods for forming conductivegrid patterns on flexible polymer sheets. The grid patterns formed may,for example, be particularly suitable for use as collection grids inphotovoltaic cells or modules or as low cost flexible circuits such asradio frequency identification tags (RFID tags).

INTRODUCTION

The field of photovoltaics generally relates to multi-layer materialsthat convert sunlight directly into DC electrical power. The basicmechanism for this conversion is the photovoltaic effect, first observedby Antoine-César Becquerel in 1839, and first correctly described byEinstein in a seminal 1905 scientific paper for which he was awarded aNobel Prize for physics. In the United States, photovoltaic (PV) devicesare popularly known as solar cells or PV cells. Solar cells aretypically configured as a cooperating sandwich of p-type and n-typesemiconductors, in which the n-type semiconductor material (on one“side” of the sandwich) exhibits an excess of electrons, and the p-typesemiconductor material (on the other “side” of the sandwich) exhibits anexcess of holes, each of which signifies the absence of an electron.Near the p-n junction between the two materials, valence electrons fromthe n-type layer move into neighboring holes in the p-type layer,creating a small electrical imbalance inside the solar cell. Thisresults in an electric field in the vicinity of the metallurgicaljunction that forms the electronic p-n junction.

When an incident photon excites an electron in the cell into theconduction band, the excited electron becomes unbound from the atoms ofthe semiconductor, creating a free electron/hole pair. Because, asdescribed above, the p-n junction creates an electric field in thevicinity of the junction, electron/hole pairs created in this mannernear the junction tend to separate and move away from the junction, withthe electron moving toward the electrode on the n-type side, and thehole moving toward the electrode on the p-type side of the junction.This creates an overall charge imbalance in the cell, so that if anexternal conductive path is provided between the two sides of the cell,electrons will move from the n-type side back to the p-type side alongthe external path, creating an electric current. In practice, electronsmay be collected from at or near the surface of the n-type side by aconducting grid that covers a portion of the surface, while stillallowing sufficient access into the cell by incident photons.

Such a photovoltaic structure, when appropriately located electricalcontacts are included and the cell (or a series of cells) isincorporated into a closed electrical circuit, forms a working PVdevice. As a standalone device, a single conventional solar cell is notsufficient to power most applications. As a result, solar cells arecommonly arranged into PV modules, or “strings,” by connecting the frontof one cell to the back of another, thereby adding the voltages of theindividual cells together in electrical series. Typically, a significantnumber of cells are connected in series to achieve a usable voltage. Theresulting DC current then may be fed through an inverter, where it istransformed into AC current at an appropriate frequency, which is chosento match the frequency of AC current supplied by a conventional powergrid. In the United States, this frequency is 60 Hertz (Hz), and mostother countries provide AC power at either 50 Hz or 60 Hz.

One particular type of solar cell that has been developed for commercialuse is a “thin-film” PV cell. In comparison to other types of PV cells,such as crystalline silicon PV cells, thin-film PV cells require lesslight-absorbing semiconductor material to create a working cell, andthus can reduce processing costs. Thin-film based PV cells also offerreduced cost by employing previously developed deposition techniques forthe electrode layers, where similar materials are widely used in thethin-film industries for protective, decorative, and functionalcoatings. Common examples of low cost commercial thin-film productsinclude water impermeable coatings on polymer-based food packaging,decorative coatings on architectural glass, low emissivity thermalcontrol coatings on residential and commercial glass, and scratch andanti-reflective coatings on eyewear. Adopting or modifying techniquesthat have been developed in these other fields has allowed a reductionin development costs for PV cell thin-film deposition techniques.

Furthermore, thin-film cells have exhibited efficiencies exceeding 20%,which rivals or exceeds the efficiencies of the most efficientcrystalline cells. In particular, the semiconductor material copperindium gallium diselenide (CIGS) is stable, has low toxicity, and istruly a thin film, requiring a thickness of less than two microns in aworking PV cell. As a result, to date CIGS appears to have demonstratedthe greatest potential for high performance, low cost thin-film PVproducts, and thus for penetrating bulk power generation markets. Othersemiconductor variants for thin-film PV technology include copper indiumdiselenide, copper indium disulfide, copper indium aluminum diselenide,and cadmium telluride.

Some thin-film PV materials may be deposited either on rigid glasssubstrates, or on flexible substrates. Glass substrates are relativelyinexpensive, generally have a coefficient of thermal expansion that is arelatively close match with the CIGS or other absorber layers, and allowfor the use of vacuum deposition systems. However, when comparingtechnology options applicable during the deposition process, rigidsubstrates suffer from various shortcomings during processing, such as aneed for substantial floor space for processing equipment and materialstorage, expensive and specialized equipment for heating glass uniformlyto elevated temperatures at or near the glass annealing temperature, ahigh potential for substrate fracture with resultant yield loss, andhigher heat capacity with resultant higher electricity cost andprocessing time for heating the glass. Furthermore, rigid substratesrequire increased shipping costs due to the weight and fragile nature ofthe glass. As a result, the use of glass substrates for the depositionof thin films may not be the best choice for low-cost, large-volume,high-yield, commercial manufacturing of multi-layer functional thin-filmmaterials such as photovoltaics.

In contrast, roll-to-roll processing of thin flexible substrates allowsfor the use of compact, less expensive vacuum systems, and ofnon-specialized equipment that already has been developed for other thinfilm industries. PV cells based on thin flexible substrate materialsalso exhibit a relatively high tolerance to rapid heating and coolingand to large thermal gradients (resulting in a low likelihood offracture or failure during processing), require comparatively lowshipping costs, and exhibit a greater ease of installation than cellsbased on rigid substrates. Additional details relating to thecomposition and manufacture of thin film PV cells of a type suitable foruse with the presently disclosed methods and apparatus may be found, forexample, in U.S. Pat. Nos. 6,310,281, 6,372,538, and 7,194,197, all toWendt et al., and U.S. Pat. No. 8,062,922 to Britt et al, all of whichare hereby incorporated by reference in their entireties.

As noted previously, a significant number of PV cells often areconnected in series to achieve a usable voltage, and thus a desiredpower output. Such a configuration is often called a “string” of PVcells. Due to the different properties of crystalline substrates andflexible thin film substrates, the electrical series connection betweencells may be constructed differently for a thin film cell than for acrystalline cell, and forming reliable series connections between thinfilm cells poses several challenges. For example, soldering (thetraditional technique used to connect crystalline solar cells) directlyon thin film cells exposes the PV coatings of the cells to damagingtemperatures, and the organic-based silver inks typically used to form acollection grid on thin film cells may not allow strong adherence byordinary solder materials in any case. Thus, PV cells often are joinedwith stand-alone wires or conductive tabs attached to the cells with anelectrically conductive adhesive (ECA), rather than by soldering.

However, even when stand-alone wires or tabs are used to form inter-cellconnections, the extremely thin coatings and potential flaking along cutPV cell edges introduces opportunities for shorting (power loss)wherever a wire or tab crosses over a cell edge. Furthermore, theconductive substrate on which the PV coatings are deposited, whichtypically is a metal foil, may be easily deformed by thermo-mechanicalstress from attached wires and tabs. This stress can be transferred toweakly-adhering interfaces, which can result in delamination of thecells.

In addition, adhesion between the ECA and the cell back side, or betweenthe ECA and the conductive grid on the front side, can be weak, andmechanical stress may cause separation of the collection grid at theselocations. Also, corrosion can occur between the molybdenum or othercoating on the back side of a cell and the ECA that joins a tab of thecollection grid to the solar cell there. This corrosion may result in ahigh-resistance contact or adhesion failure, leading to power losses.

Advanced methods of joining thin film PV cells with conductive tabs orribbons may largely overcome the problems of electrical shorting anddelamination, but may require undesirably high production costs to doso. Furthermore, all such methods—no matter how robust—require that atleast some portion of the PV string be covered by a conductive tab,which blocks solar radiation from striking that portion of the stringand thus reduces the efficiency of the system. As a result, there is aneed for improved methods of interconnecting PV cells into strings, andfor improved strings of interconnected cells. Specifically, there is aneed for strings and methods of their formation that reduceinterconnection costs and reduce the fraction of each PV cell that iscovered by the interconnection mechanism, while maintaining or improvingthe ability of the cell to withstand stress.

ICI (Integrated Cell Interconnect) technology overcomes the aboveproblem, but presently relies upon a Cu grid collection structure formedin a subtractive process. Cu foil formed by electrodeposition islaminated on a polymer web, and more than 90% of the Cu mass issubsequently removed. The relative area of Cu removed is even greater.While a portion of the Cu that is removed can be reclaimed, the processis relatively costly and inefficient, and only a few suppliers worldwideare capable of supplying the flexible interconnect structure produced inthis manner. Furthermore, the reclaimed Cu must be refined andreprocessed for applications requiring particular levels of purity.

In addition, the plating and subtractive etching process associated withthe formation of current grid structures utilizes strong chemical bathsthat can adulterate the substrate (affecting solar module performance orreliability), or place constraints on suitable substrate materials.

For all of the above reasons, there is a need for improved apparatus andmethods for forming conductive grid patterns on flexible substrates suchas transparent polymer sheets.

SUMMARY

The present disclosure provides systems, apparatuses, and methodsrelating to conductive grid formation on polymer sheets. In someembodiments, a method of forming a conductive metal grid on atransparent polymer sheet may include applying an electricallyinsulating coating to an electrically conductive cylinder, wherein thecoating is patterned to expose portions of a conductive surface of thecylinder corresponding to a grid pattern to be formed; at leastpartially immersing the cylinder into a metal-containing solution;applying electrical current to the conductive cylinder, thereby causingelectrodeposition of metal onto the exposed portions of the conductivesurface and forming a conductive metal grid on the cylinder; rotatingthe cylinder until the conductive grid comes into contact with atransparent polymer sheet wrapped around a portion of the cylinder; andseparating the sheet from the cylinder with the conductive grid attachedto the sheet.

In some embodiments, a method of forming a conductive collection gridfor a photovoltaic module may include applying an electricallyinsulating coating to a drum having an electrically conductive surface;patterning the electrically insulating coating to expose areas of theconductive surface of the drum corresponding to a grid pattern;electrodepositing a metal onto the exposed areas of the conductivesurface to form a metallic collection grid attached to the conductivesurface; contacting the collection grid with a transparent polymer sheetwhile the collection grid is attached to the conductive surface, therebycausing the collection grid to adhere to the polymer sheet; andseparating the transparent polymer sheet from the drum with the gridpattern attached to the polymer sheet.

In some embodiments, a method of forming a conductive grid on atransparent flexible sheet, comprising: providing an electricallyconductive surface partially covered with an electrically insulatingcoating, wherein an uncovered portion of the conductive surfacecorresponds to a grid pattern; electrodepositing a conductive materialonto the uncovered portion of the conductive surface to form aconductive grid attached to the conductive surface; contacting theelectrically insulating coating and the conductive grid with atransparent flexible sheet; and separating the transparent flexiblesheet from the electrically insulating coating with the conductive gridattached to the transparent flexible sheet.

In some embodiments, a high-rate, low cost additive method of forming aconductive metallic grid of arbitrary complexity on a transparentadhesive polymer sheet may include using an electrically insulating,non-stick coating on a metallic cylinder, said insulating coating firstpatterned to expose the conductive surface of the metallic cylinder inpreselected areas; at least partially immersing the cylinder in achemical solution wherein a conductive metal is electrodeposited intothe features patterned in the insulating layer; pulling off theelectrodeposited metallic grid electrodeposited into the areas patternedto expose the conductive metallic cylinder onto an adhesive polymersheet as the adhesive polymer sheet is wrapped around a portion of theouter circumference of said cylinder; and separating the polymer sheetfrom the cylinder, creating a formed metallic grid adherent to theadhesive polymer sheet.

Features, functions, and advantages may be achieved independently invarious embodiments of the present disclosure, or may be combined in yetother embodiments, further details of which can be seen with referenceto the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an illustrative apparatus for forming aconductive grid on a transparent polymer sheet.

FIG. 2 is a magnified partial view of an illustrative conductive gridpattern formed on a transparent polymer sheet in accordance with aspectsof the present disclosure.

FIG. 3 is a flow chart depicting steps performed in an illustrativemethod of forming a conductive metal grid on a transparent polymersheet.

FIG. 4 is a flow chart depicting steps performed in an illustrativemethod of forming a conductive collection grid for a photovoltaicmodule.

FIG. 5 is a flow chart depicting steps performed in an illustrativemethod of forming a conductive grid on a transparent flexible sheet.

DESCRIPTION

Overview

Various embodiments of a system for additively forming a conductive gridon a transparent adhesive polymer sheet (or any other suitable polymersheet), as well as related methods, are described below and illustratedin the associated drawings. Unless otherwise specified, a grid formationsystem and/or its various components may, but are not required to,contain at least one of the structure, components, functionality, and/orvariations described, illustrated, and/or incorporated herein.Furthermore, the process steps, structures, components, functionalities,and/or variations described, illustrated, and/or incorporated herein inconnection with the present teachings may, but are not required to, beincluded in other similar grid formation systems. The followingdescription of various embodiments is merely exemplary in nature and isin no way intended to limit the disclosure, its application, or uses.Additionally, the advantages provided by the embodiments, as describedbelow, are illustrative in nature and not all embodiments provide thesame advantages or the same degree of advantages.

Grid formations systems disclosed herein overcome several disadvantagesinherent in typical grid formation techniques. For example, existing Cudeposition and subtractive etching methods result in high percentages ofunrecoverable waste and potential substrate adulteration. In contrast,additive grid formation methods described herein result in low ornegligible waste, and do not subject the substrate (i.e., the polymersheet) to potentially harmful chemical baths.

In general, an additive grid formation system may include a rotatabledrum having an electrically conductive outer surface coated with anon-stick, insulating layer, e.g., polytetrafluoroethylene (PTFE). Agrid pattern may be formed in the insulating layer, such that theunderlying conductive surface is exposed where the grid pattern exists.The drum may be partially submerged in a chemical bath containing aconductive metal (e.g., copper ions), with the axis of the drum beingsubstantially parallel to the surface of the bath. A lower portion ofthe drum may be submerged, while an upper portion remains out of thebath, such that rotation of the drum causes the patterned outer surfaceof the drum to pass into and subsequently out of the bath.

An electrical current may be applied, resulting in electrodeposition ofthe Cu (or other conductive metal) onto the submerged portion of thedrum. However, as the surface other than the grid pattern is covered inan insulating material, Cu is deposited only onto the exposed gridpattern.

A transparent polymer sheet, which may have an adhesive surface, may beplaced into contact with an unsubmerged portion of the rotating drum.The sheet may come into contact with the drum after the drum surfaceexits the bath, and wrap around an unsubmerged portion of the drum. Thesheet may then be removed from the drum surface prior to its reentryinto the bath. Pressure and/or heat may be applied, such that the sheetis laminated onto the surface of the drum, and then peeled off uponexit. This lamination and subsequent separation results in the Cu gridbeing attached to the polymer sheet and removed from the drum surface.An electrically conductive coating may be added to the exposed gridpattern of the drum, such that the coating functions as a release layerto facilitate the grid preferentially attaching to the polymer sheet.

The polymer sheet may comprise a roll or spool of polymer sheetmaterial, or another substantially continuous source of polymersheeting. Accordingly, the polymer sheet may be continuously fed ontoand off of the drum as the drum is rotated into and out of the chemicalbath, such that a continuous polymer sheet having an electricallyconductive grid is produced by the system. The system may comprise aroll-to-roll system, such that the metalized sheet is spooled onto areceiving roll.

Examples, Components, and Alternatives

The following sections describe selected aspects of exemplary gridformation systems as well as related systems and/or methods. Theexamples in these sections are intended for illustration and should notbe interpreted as limiting the entire scope of the present disclosure.Each section may include one or more distinct inventions, and/orcontextual or related information, function, and/or structure.

Illustrative Apparatus

As shown in FIGS. 1-2, this section of the present disclosure relates toan illustrative apparatus that may be used to form a conductive metalgrid on a transparent polymer sheet.

FIG. 1 depicts an example of a grid formation apparatus, generallyindicated at 100, for forming a conductive metal grid 102 on atransparent polymer sheet 104. Apparatus 100 includes a bath container106, an electrically conductive cylinder 108, compressing elements 110,112, 114, 116 disposed on portions of cylinder 108, and heaters 118 and120. Heater 118 is disposed inside cylinder 108 in the vicinity ofcompressing elements 110 and 112. Heater 120 is disposed insidecompressing element 110.

Bath container 106 is configured to contain a metal-containingelectrodeposit solution 122, and may include any suitable structures andcomponents configured to receive cylinder 108 at least partially intothe solution. For instance, the bath container may include walls 124,126, 128, 130 and a floor 132 configured to contain electrodepositsolution 122. Bath container 106 forms an open surface, generallyindicated at 134, configured to receive electrically conductive cylinder108. Bath container 106 may comprise any electrically neutral material.For instance, bath container 106 may be made of plastic. In some cases(not shown), the entirety of apparatus 100 may be enclosed.

Electrodeposit solution 122, also referred to as a metal-containingsolution, may have any suitable composition configured to transport anelectrodepositable ion or a combination of electrodepositable ions. Forexample, electrodeposit solution 122 may be an aqueous solutioncontaining copper ions, copper ions plus some other metallic ion such asnickel or chromium, or any other suitable metallic ion or combination ofions. The ions in solution 122 will generally be provided from one ormore sources of material (not shown) which are immersed in the solutionand which function as an electrical anode, as is well known in the artof electrodeposition.

Electrically conductive cylinder 108, which also may be referred to as adrum, a barrel, and/or a mandrel, may include any suitable structuresand components configured to conduct an applied electrical current andto rotate about an axis. For instance, electrically conductive cylinder108 may be a stainless steel or aluminum cylinder having a conductivesurface 136. Cylinder 108 may be configured to rotate partially withinsolution 122, as shown in FIG. 1. The electrically conductive cylinderhas an electrically insulating coating 138 that is patterned to exposeportions of conductive surface 136. In some cases, cylinder 108 may behollow, as depicted in FIG. 1, whereas in other cases the cylinder maybe substantially solid or partially solid in its interior. In someexamples, cylinder 108 may rotate about a central axle (not shown). Insome cases, rotation of cylinder 108 may be driven by the motion ofpolymer sheet 104. In other cases, cylinder 108 may be rotated in someother manner, such as by rotation of a central axle which is rigidlyattached to the cylinder.

Electrically insulating coating 138 may include any suitable structuresand components configured to provide electrical insulation, inertness tothe electrodeposition chemistry, adhesion to cylinder 108, non-adhesionor low-adhesion to transparent polymer sheet 104 under laminationconditions, and resistance to lamination temperatures (around 160° C.).For example, the electrically insulating coating may be made offluoropolymer, chlorofluoropolymer, or any other suitable thermosettingor thermoplastic polymer. In some examples, electrically insulatingcoating 138 may comprise PTFE. The coating may have any desiredthickness approximately corresponding to the desired thickness of aconductive grid to be created. The coating thickness may be chosen tocontrol the thickness of the grid, as measured radially with respect tothe cylinder. For example, the coating may be less than about 50micrometers (i.e., microns) thick, and in some cases the coating may beapproximately 25 to approximately 30 microns thick.

Patterning of the electrically insulating coating can be accomplished,for example, via laser, which is used to selectively remove theinsulating coating down to the underlying conductive surface. Aresulting pattern, generally indicated at 140, may include lines andinterconnection regions with various dimensions. Any arbitrary patternmay be formed, resulting in great flexibility of design. In someexamples, pattern 140 may correspond to a desired conductive grid 102configured to electrically interconnect pairs of adjacent photovoltaic(PV) cells. For instance, pattern 140 may include fine parallellongitudinal lines, thicker transverse lines, and interconnectionregions, respectively forming the shapes of grid lines 142, bus bars144, and interconnection regions 146 of grid 102, described furtherbelow with respect to FIG. 2.

Compressing elements 110, 112, 114, 116 are configured to guide andcompress a transparent polymer sheet, such as sheet 104, againstcylinder 108. For example, compressing elements 110, 112, 114, 116 mayinclude nip rolls or pinch rolls (or rollers), and may be smaller,paired cylinders arranged adjacent to cylinder 108. In the exampledepicted in FIG. 1, a first pair of pinch rolls 110 and 112 is disposedon opposite sides of (i.e., above and below) conductive surface 136, atthe desired position where sheet 104 is to contact surface 136. In otherwords, one compressing element (110) may be exterior to cylinder 108,and the other compressing element (112) may be interior to the cylinder.Similarly, a second pair of pinch rolls 114 and 116 is disposed onopposite sides of surface 136 downstream of the first pair, at a desiredposition where sheet 104 is to separate from contact surface 136.Accordingly, sheet 104 wraps around a portion of cylinder 108 betweenthe two pairs of rolls. In some examples, the weight of cylinder 108 maybe supported by lower compressing elements 112 and 116, and/or rotationof cylinder 108 may be driven by the compressing elements, rotation ofwhich may in turn be driven in some cases by motion of sheet 104. Insome examples, one or both interior rolls may be absent, such as whencylinder 108 is supported on a central axle and pressure is applied fromexterior rolls to achieve lamination.

As indicated above, a first space between compressing element 110 andconductive surface 136 forms an entry 148 for transparent sheet 104,while a second space between compressing element 114 and conductivesurface 136 forms an exit 150 for transparent sheet 104. Rotation ofcylinder 106, generally indicated at 152, will result in rotation ofcompressing elements 110-116 (or, in some examples, vice versa) causingsheet 104 to be compressed against cylinder 106 at entry 148. Thisrotation also allows sheet 104 to be lifted away from cylinder 106 atexit 150. In conjunction with compression produced by the nip rolls, theapplication of suitable tension to the polymer sheet will cause thesheet to remain compressed against the cylinder in an intermediateregion 154 between the entry point and the exit point.

In addition to pressure from the compressing elements, lamination ofsheet 104 onto the drum may be aided by an adhesive layer on sheet 104(and/or on cylinder 108), and/or by application of heat. In someexamples, heat is applied without additional adhesive. In some examples,an adhesive is used to facilitate transfer of the conductive grid ontothe polymer sheet. For example, a thermoplastic adhesive may be used,which may be activated by heating. One or more heaters may be utilizedfor any of these purposes. Such heaters may include any suitabledevice(s) configured to generate lamination temperatures with respect totransparent polymer sheet 104. For example, first heater 120 may bedisposed interior to compression element 110, and second heater 118 maybe disposed interior to cylinder 108. Heaters 118 and 120 may includeinduction heater elements and/or resistive elements used to generatetemperatures around 160° C. In general, heaters 118 and 120 may be usedto raise the temperatures of the polymer sheet, the exterior nip rolland/or the main cylinder in the vicinity of entry point 148.

As shown in FIG. 1, metal grid 102 is formed on cylinder 108 and sticksto, adheres to, and/or is laminated onto sheet 104 in intermediateregion 154. The grid is then removed from cylinder 108 as sheet 104 ispeeled off the drum at or near exit 150. A release layer or releasesurface may be applied to the exposed conductive surfaces of pattern 140to facilitate release of the grid material from the drum. For example,this release layer may include electroplated chromium, nickel-teflon,chromium-polymer, and/or other similar conductive layers that may beapplied selectively to the exposed conductive mandrel surfaces.

The combination of metal grid 102 and sheet 104 forms a flexiblemetalized sheet 156, which is then usable, e.g., for further PVmanufacturing, such as in flexible PV panels. Metalized sheet 156 may bereferred to as a metalized polymer sheet and/or a conductive gridlaminate or grid layer.

Turning to FIG. 2, a magnified partial view of metalized sheet 156 isdepicted, illustrating possible details of a grid pattern that may beformed on a polymer sheet according to aspects of the present teachings.Here, grid 102 is shown on polymer sheet 104 to include grid lines 142,bus bars 144, and interconnection regions 146. More generally, anysuitable metalized grid pattern may be formed on a flexible substrateusing the methods and apparatus of the present teachings.

Transparent polymer sheet 104 is configured to provide selectiveadhesion, flexibility, and resistance to lamination temperatures. Forexample, when transparent polymer sheet 104 is heated by heaters 118 and120, the sheet may adhere to metal grid 102 newly formed on cylinder 106but not to electrically insulating coating 138. Transparent polymersheet 104 may be made of a thermoplastic polymer such as thermoplasticpolyolefin/polyethylene terephthalate (TPO/PET) or the like.

Grid 102 is composed of electrodeposited metal, forming grid lines 142,bus bars 144, and interconnection regions 146. The grid geometry shownin FIG. 2 is merely illustrative and should not be considered limiting.Grid lines, bus bars and interconnection regions may have differentdimensions corresponding to a desired grid configured to electricallyinterconnect adjacent photovoltaic cells of a particular type, or insome cases simply to collect electric current generated by a singlecell.

In the embodiment of FIG. 2, grid lines 142 are fine parallel linesextending longitudinally in rectangular loops from bus bar 144. Gridlines 142 typically have a width below about 200 microns and a thicknessbelow about 50 microns.

Bus bar 144 interconnects grid lines 142. Bus bar 144 has a widthsubstantially greater than width of the grid lines, and like the gridlines typically has a thickness below 50 microns. The size of the gridpattern may be varied as needed, for example to accommodate different PVcell dimensions.

Interconnection regions 146 include transverse extensions of bus bar144. In the embodiment of FIG. 2, region 146 is configured to extendbeyond the boundary of a first PV cell contacted by the correspondingbus bar, to make contact with a portion of an adjacent, second PV cell.By appropriately electrically isolating these portions of the adjacentcell, and causing interconnection regions 146 to make electrical contactwith a back contact of the adjacent cell, grid 102 can be used toelectrically interconnect adjacent cells in series. The grid lines, thebus bars, and the interconnection regions will generally have the samethickness of electrodeposited metal, which as mentioned previously istypically less than 50 microns and may correspond to a thickness ofcoating layer 138.

Illustrative Methods

This section describes steps performed in various methods for formingmetalized grids on polymer sheets; see FIGS. 3-5. Aspects of gridformation apparatus 100 may be utilized in the method steps describedbelow. Where appropriate, reference may be made to previously describedcomponents and systems that may be used in carrying out each step. Thesereferences are for illustration, and are not intended to limit thepossible ways of carrying out any particular step of the method.

FIG. 3 is a flowchart illustrating operations performed in anillustrative method, and may not recite the complete process or allsteps of the method. FIG. 3 depicts multiple steps of a method,generally indicated at 200, which may be performed in conjunction withgrid formation systems in accordance with aspects of the presentdisclosure. Although various steps of method 200 are described below anddepicted in FIG. 3, the steps need not necessarily all be performed, andin some cases may be performed in a different order than the ordershown.

Step 202 includes applying an electrically insulating coating to aconductive cylinder, leaving portions of the cylinder exposed in a gridpattern. For example, an insulating coating such as PTFE may be appliedto a conductive drum, with a grid pattern formed in the coating toexpose the conductive drum underneath. The grid pattern may beconfigured as one or more electrical circuits for PV cells. The gridpattern in the coating may be formed, for example, by laser etching thepattern after the coating has been applied to the drum. In other cases,the grid pattern may be formed by chemically or physically masking theconductive drum before applying the insulating coating, followed byremoval of the masking agent.

Step 204 includes applying a conductive release layer to the exposedportions of the conductive cylinder. For example, the portions that areexposed, i.e., the grid pattern in the coating, may have a releasingmaterial applied. Accordingly, metal will be deposited (see step 208)into the grid pattern, but the metal will be less likely to remainadhered or otherwise attached to the exposed conductive portions of thecylinder when contacted by a polymer sheet. Suitable release materialsinclude chromium, nickel-teflon, chromium-polymer, and/or the like,which may be applied, for example, by electrodeposition. The releaselayer is applied as a thin coating, leaving an etched pattern having adepth similar to the desired thickness of the grid pattern to be formedand eventually applied to a flexible sheet.

Step 206 includes at least partially immersing the cylinder into ametal-containing solution. For example, the cylinder may be partiallyimmersed in a radial direction, such that the entire length of thecylinder is submerged, but not the entire diameter. Although the drum ofthe apparatus is described here as a cylinder, any suitable shape may beused. The cylinder may remain so immersed during subsequent steps.

Step 208 includes applying electrical current to the conductive cylinderto cause electrodeposition of a conductive grid. Any suitableelectrodeposition method may be used, such that a metal in themetal-containing solution is deposited into the grid pattern of thecylinder, thereby forming the conductive grid.

Step 210 includes rotating the cylinder until the conductive grid comesinto contact with a transparent polymer sheet. Rotation of the cylindermay be achieved by any suitable method or device. For example, amotorized drive unit may be used to rotate the cylinder directly, e.g.,at a selected rotational speed. In other cases, the polymer sheet may betransported, for instance by a reel-to-reel system, and friction betweenthe polymer sheet and the cylinder may cause the cylinder to rotate at arate set by the movement of the sheet.

Step 212 includes heating the transparent polymer sheet. The polymersheet may be heated directly or indirectly. For example, a roller orother component may be heated and placed into contact with the sheet,whereby heat is transferred to the sheet. In other cases, the sheet maybe heated directly, with a dedicated heater, before or after it makescontact with the conductive cylinder.

Step 214 includes heating at least a portion of the conductive cylinder.For example, the conductive cylinder may be heated in a region of thecylinder adjacent to the location where the conductive grid comes intocontact with the polymer sheet. Any suitable heating mechanism may beused to heat the cylinder. For example, an inductive heating element maybe disposed in a fixed location near the cylinder, adjacent or in closeproximity to the outer surface.

Step 216 includes compressing the transparent polymer sheet against thecylinder. Compression may be accomplished by any suitable mechanism. Forexample, a pair of nip rolls or pinch rollers may be utilized, with oneroll on an exterior surface of the sheet and the opposing roll on aninterior surface of the cylinder. In some examples, only an exteriorroller may be used to apply compression, wherein the cylinder itselfprovides opposing pressure. Compression is performed in this step tolaminate the polymer sheet onto the outer surface of the cylinder. Ingeneral, the conductive grid will preferentially adhere to the polymersheet rather than to the conductive cylinder. One or more adhesives maybe utilized on the polymer sheet to aid this process. The adhesive maybe heat activated.

Step 218 includes cooling the transparent polymer sheet. Any suitablecooling method may be used, e.g., forced air cooling, refrigeration,and/or the like. Passive (e.g., dissipation through ordinary conduction,radiation, and convection) and/or active cooling methods may beutilized. This solidifies the thermoplastic adhesive to theelectrodeposited metal grid and reduces the adhesion of the polymersheet to the portions of the conductive cylinder surrounding the gridpattern, and/or adhesion of the grid pattern to the underlying releaselayer.

Step 220 includes separating the sheet from the cylinder with theconductive grid attached to the sheet. Separation may be performed byurging or otherwise pulling the sheet in a direction transverse to thecylinder surface. Separation force may be supplied by powered mechanicalequipment, such as a powered spindle, spooling apparatus, or conveyor.Through a proper balance of adhesion forces between the polymer sheet,the conductive grid pattern, and the cylinder, the result of theseparation will be that substantially the entirety of the grid patternwill be adhered to the polymer sheet.

FIG. 4 is a flowchart illustrating operations performed in anotherillustrative method, and may not recite the complete process or allsteps of the method. FIG. 4 depicts multiple steps of a method,generally indicated at 300, which may be performed in conjunction withgrid formation systems in accordance with aspects of the presentdisclosure. Although various steps of method 300 are described below anddepicted in FIG. 4, the steps need not necessarily all be performed, andin some cases may be performed in a different order than the ordershown.

Step 302 includes applying an electrically insulating coating to a drumhaving an electrically conductive surface. For example, the drum mayhave a metal surface, such as steel or aluminum. The drum may have anysuitable shape. For example, the drum may be cylindrical or tubular. Insome examples, the drum may have an oval or polygonal cross section. Theelectrically insulating coating may have low-friction, non-stick, and/orelectrically neutral characteristics. The electrically insulatingcoating may include any suitable material, such as PTFE.

Step 304 includes patterning the electrically insulating coating toexpose areas of the conductive surface of the drum corresponding to agrid pattern. For example, the coating may be etched, masked, orotherwise formed into a grid pattern corresponding to electricalcircuits for a PV cell or string of cells.

Step 306 includes applying a thin release layer coating to the exposedareas of the conductive surface. Suitable release layers may includechromium, nickel-teflon, chromium-polymer, and/or the like, which may beapplied by electrodeposition or by any other suitable method. Therelease layer may be applied with any desired thickness. For instance,if the electrically insulating coating has a first thickness, therelease layer will generally have a second thickness less than the firstthickness, and the difference between the first thickness and the secondthickness will be similar to a desired thickness of the conductive gridto be formed.

Step 308 includes electrodepositing a metal onto the exposed areas ofthe conductive surface to form a metallic collection grid attached tothe conductive surface. Any suitable electrodeposition method may beused, and any suitable conductive metal. For example, a chemical bathcontaining copper ions may be utilized.

Step 310 includes heating a transparent polymer sheet and/or theconductive surface of the drum. Any suitable heaters may be used, asdescribed above. Heating may be performed to facilitate the laminationof step 312, and in some cases may activate an adhesive applied to thesheet, the drum, or both.

Step 312 includes contacting the collection grid with the transparentpolymer sheet. This may be achieved through a lamination process inwhich the polymer sheet is laminated to the grid using pressure,adhesive, and/or heat.

Step 314 includes cooling the transparent polymer sheet. As describedabove, any suitable method may be used, such as forced air cooling,refrigeration, and/or the like. Passive (e.g., dissipation) and/oractive cooling methods may be utilized.

Step 316 includes separating the transparent polymer sheet from the drumwith the grid pattern attached to the polymer sheet.

FIG. 5 is a flowchart illustrating operations performed in anotherillustrative method, and may not recite the complete process or allsteps of the method. FIG. 5 depicts multiple steps of a method,generally indicated at 400, which may be performed in conjunction withgrid formation systems in accordance with aspects of the presentdisclosure. Although various steps of method 400 are described below anddepicted in FIG. 5, the steps need not necessarily all be performed, andin some cases may be performed in a different order than the ordershown.

Step 402 includes providing an electrically conductive surface partiallycovered with an electrically insulating coating. The electricallyconductive surface may include a surface of an electrically conductivedrum. The insulating coating may include a layer of substantially inertmaterial.

Step 404 includes applying a release layer onto the uncovered portion ofthe conductive surface, still leaving the formerly uncovered portion ofthe conductive surface at a depth below the surface of the electricallyinsulating coating by a desired amount. Suitable release materialsinclude chromium, nickel-teflon, chromium-polymer, and/or the like.

Step 406 includes electrodepositing a conductive material onto theuncovered portion of the conductive surface to form a conductive grid.See discussion of suitable electrodeposition methods above.

Step 408 includes heating a transparent flexible sheet. For example,step 408 may include heating a flexible polymer sheet, e.g., using oneor more heating elements and/or heated components.

Step 410 includes contacting the electrically insulating coating and theconductive grid with the transparent flexible sheet. As above, this stepmay include lamination of the sheet onto the coating and grid, possiblywith the aid of pressure, adhesive, and/or heat.

Step 412 includes cooling the transparent flexible sheet. As describedabove, any suitable method may be used, such as forced air cooling,refrigeration, and/or the like. Passive (e.g., dissipation) and/oractive cooling methods may be utilized.

Step 414 includes separating the transparent flexible sheet from theelectrically insulating coating with the conductive grid attached to thesheet.

In another embodiment, a method of forming a conductive metal grid on atransparent polymer sheet may include applying an electricallyinsulating coating to an electrically conductive cylinder, wherein thecoating is patterned to expose portions of a conductive surface of thecylinder corresponding to a grid pattern to be formed. The cylinder maybe immersed, at least partially, into a metal-containing solution.Electrical current may be applied to the conductive cylinder, therebycausing electrodeposition of metal onto the exposed portions of theconductive surface and forming a conductive metal grid on the cylinder.The cylinder may be rotated until the conductive grid comes into contactwith a transparent polymer sheet wrapped around a portion of thecylinder. The sheet may be separated from the cylinder with theconductive grid attached to the sheet.

In another embodiment, a method of forming a conductive collection gridfor a photovoltaic module may include applying an electricallyinsulating coating to a drum having an electrically conductive surface.The electrically insulating coating may be patterned to expose areas ofthe conductive surface of the drum corresponding to a grid pattern. Ametal may be electrodeposited onto the exposed areas of the conductivesurface to form a metallic collection grid attached to the conductivesurface. The collection grid may be contacted with a transparent polymersheet while the collection grid is attached to the conductive surface,thereby causing the collection grid to adhere to the polymer sheet. Thetransparent polymer sheet may be separated from the drum with the gridpattern attached to the polymer sheet.

In another embodiment, a method of forming a conductive grid on atransparent flexible sheet may include providing an electricallyconductive surface partially covered with an electrically insulatingcoating, wherein an uncovered portion of the conductive surfacecorresponds to a grid pattern. A conductive material may beelectrodeposited onto the uncovered portion of the conductive surface toform a conductive grid attached to the conductive surface. Theelectrically insulating coating and the conductive grid may be contactedwith a transparent flexible sheet. The transparent flexible sheet may beseparated from the electrically insulating coating with the conductivegrid attached to the transparent flexible sheet.

Selected Examples

This section describes additional aspects and features of grid formationsystems and methods, presented without limitation as a series ofparagraphs, some or all of which may be alphanumerically designated forclarity and efficiency. Each of these paragraphs can be combined withone or more other paragraphs, and/or with disclosure from elsewhere inthis application, in any suitable manner. Some of the paragraphs belowexpressly refer to and further limit other paragraphs, providing withoutlimitation examples of some of the suitable combinations.

A0. A method of forming a conductive metal grid on a transparent polymersheet, comprising: applying an electrically insulating coating to anelectrically conductive cylinder, wherein the coating is patterned toexpose portions of a conductive surface of the cylinder corresponding toa grid pattern to be formed; at least partially immersing the cylinderinto a metal-containing solution; applying electrical current to theconductive cylinder, thereby causing electrodeposition of metal onto theexposed portions of the conductive surface and forming a conductivemetal grid on the cylinder; rotating the cylinder until the conductivegrid comes into contact with a transparent polymer sheet wrapped arounda portion of the cylinder; and separating the sheet from the cylinderwith the conductive grid attached to the sheet.

A1. The method of paragraph A0, further comprising heating thetransparent polymer sheet, thereby increasing adhesion between the sheetand the conductive grid.

A1a. The method of paragraph A1, further comprising adding aheat-activated adhesive to the transparent polymer sheet

A2. The method of any of paragraphs A0 through A1a, further comprisingheating the portion of the cylinder around which the transparent polymersheet is wrapped, thereby increasing adhesion between the sheet and theconductive grid.

A3. The method of paragraph A2, further comprising cooling thetransparent polymer sheet prior to separating the sheet from thecylinder.

A4. The method of any of paragraphs A0 through A3, further comprisingcompressing the transparent polymer sheet against the cylinder, therebyincreasing adhesion between the sheet and the conductive grid.

A5. The method of any of paragraphs A0 through A4, wherein theelectrically insulating coating is formed from a syntheticfluoropolymer.

A6. The method of paragraph A5, wherein the electrically insulatingcoating is formed from polytetrafluoroethylene (PTFE).

A7. The method of any of paragraphs A0 through A6, further comprisingapplying a conductive release layer to the exposed portions of theconductive surface of the cylinder.

B0. A method of forming a conductive collection grid for a photovoltaicmodule, comprising: applying an electrically insulating coating to adrum having an electrically conductive surface; patterning theelectrically insulating coating to expose areas of the conductivesurface of the drum corresponding to a grid pattern; electrodepositing ametal onto the exposed areas of the conductive surface to form ametallic collection grid attached to the conductive surface; contactingthe collection grid with a transparent polymer sheet while thecollection grid is attached to the conductive surface, thereby causingthe collection grid to adhere to the polymer sheet; and separating thetransparent polymer sheet from the drum with the grid pattern attachedto the polymer sheet.

B1. The method of paragraph B0, wherein the electrically insulatingcoating is formed from polytetrafluoroethylene (PTFE).

B2. The method of any of paragraphs B0 through B1, further comprisingheating at least one of the transparent polymer sheet and the conductivesurface, thereby increasing adhesion between the transparent polymersheet and the collection grid.

B3. The method of paragraph B2, further comprising cooling thetransparent polymer sheet before separating the transparent polymersheet from the drum.

B4. The method of any of paragraphs B0 through B3, further comprisingapplying a release layer to the exposed areas of the conductive surface.

B5. The method of paragraph B4, wherein the release layer is formed froma material chosen from the set consisting of chromium, nickel-teflon,and chromium-polymer.

C0. A method of forming a conductive grid on a transparent flexiblesheet, comprising: providing an electrically conductive surfacepartially covered with an electrically insulating coating, wherein anuncovered portion of the conductive surface corresponds to a gridpattern; electrodepositing a conductive material onto the uncoveredportion of the conductive surface to form a conductive grid attached tothe conductive surface; contacting the electrically insulating coatingand the conductive grid with a transparent flexible sheet; andseparating the transparent flexible sheet from the electricallyinsulating coating with the conductive grid attached to the transparentflexible sheet.

C1. The method of paragraph C0, wherein the electrically conductivesurface is cylindrical.

C2. The method of paragraph C1, wherein the electrically conductivesurface is configured to rotate so that each portion of the surfaceenters a solution where electrodeposition occurs and then exits thesolution before being contacted with the transparent flexible sheet.

C3. The method of any of paragraphs C0 through C2, further comprisingheating the transparent flexible sheet to promote adhesion between thesheet and the conductive grid.

C4. The method of paragraph C3, further comprising cooling thetransparent flexible sheet prior to pulling the sheet away from theelectrically insulating coating.

C5. The method of any of paragraphs C0 through C4, further comprisingapplying a release layer onto the uncovered portion of the conductivesurface, prior to electrodepositing the conductive material.

D0. A high-rate, low cost additive method of forming a conductivemetallic grid of arbitrary complexity on a transparent adhesive polymersheet may include using an electrically insulating, non-stick coating ona metallic cylinder, said insulating coating first patterned to exposethe conductive surface of the metallic cylinder in preselected areas; atleast partially immersing the cylinder in a chemical solution wherein aconductive metal is electrodeposited into the features patterned in theinsulating layer; pulling off the electrodeposited metallic gridelectrodeposited into the areas patterned to expose the conductivemetallic cylinder onto an adhesive polymer sheet as the adhesive polymersheet is wrapped around a portion of the outer circumference of saidcylinder; and separating the polymer sheet from the cylinder, creating aformed metallic grid adherent to the adhesive polymer sheet.

D1. The method of paragraph D0 using copper as the metallicelectrodeposited material to form the conductive grid.

D2. The method of any of paragraphs D0 through D1, using a thermoplasticadhesive for which a portion of the metallic cylinder or a part of thepolymer sheet, or both, are heated to activate the adhesive propertiesof said thermoplastic adhesive to facilitate transferring theelectrodeposited metallic features from the cylinder onto the polymersheet.

D3. The method described in any of paragraphs D0 through D2, in whichthe polymer sheet is replaced by a roll of polymer web, enabling acontinuous roll-to-roll process.

D4. The method of any of paragraphs D0 through D3, wherein a thinconductive coating is applied selectively in the patterned features ontothe conductive cylinder as a ‘release surface’ that facilitatestransferring the electrodeposited metallic pattern from the cylinder ormandrel onto the adhesive polymer film.

D5. The method of paragraph D4 wherein a release surface is created onthe mandrel surface in the patterned features using electroplatedchromium, nickel-teflon, chromium-polymer or other similar conductivelayers that can be applied selectively to exposed conductive mandrelsurfaces.

E0. A method of forming a conductive metallic grid of arbitrarycomplexity on a transparent adhesive polymer sheet by using anelectrically insulating, non-stick coating on a metallic cylinder, saidinsulating coating first patterned to expose the conductive surface ofthe metallic cylinder in preselected areas, which is immersed in achemical solution wherein a conductive metal is electrodeposited intothe features patterned in the insulating layer, after which theelectrodeposited metallic grid electrodeposited into the areas patternedto expose the conductive metallic cylinder is pulled off of thepatterned cylinder onto an adhesive polymer sheet as the adhesivepolymer sheet is wrapped around a portion of the outer circumference ofsaid cylinder, and then separated from the cylinder, creating a formedmetallic grid adherent to the adhesive polymer sheet.

Advantages, Features, Benefits

The different embodiments of the grid formation system described hereinprovide several advantages over known solutions for forming conductivegrids on polymer sheets. For example, illustrative embodiments describedherein allow Cu to be deposited in an additive process, only whereneeded, with very little waste. In some examples, only the Cu anodematerial may be consumed, resulting in indefinite use of solutionchemicals.

Additionally, and among other benefits, illustrative embodimentsdescribed herein allow improved PV efficiency, due to lower resistiveand optical losses.

Additionally, and among other benefits, illustrative embodimentsdescribed herein allow generation of patterns of arbitrary complexity,including bus and connection areas, with high dimensional accuracy.There may be no substantive constraints on pattern connections whileforming the grid.

Additionally, and among other benefits, illustrative embodimentsdescribed herein allow a clean, simple, low-temperature, high-throughputprocess. The process may be roll-to-roll.

Additionally, and among other benefits, illustrative embodimentsdescribed herein allow control over the cross-sectional profile of theconductor grid elements.

Additionally, and among other benefits, illustrative embodimentsdescribed herein allow easily changed patterns simply by changingpatterned drums.

No known system or device can perform these functions or combination offunctions. However, not all embodiments described herein provide thesame advantages or the same degree of advantage.

CONCLUSION

The disclosure set forth above may encompass multiple distinct exampleswith independent utility. Although each of these has been disclosed inits preferred form(s), the specific embodiments thereof as disclosed andillustrated herein are not to be considered in a limiting sense, becausenumerous variations are possible. To the extent that section headingsare used within this disclosure, such headings are for organizationalpurposes only. The subject matter of the invention(s) includes all noveland nonobvious combinations and subcombinations of the various elements,features, functions, and/or properties disclosed herein. The followingclaims particularly point out certain combinations and subcombinationsregarded as novel and nonobvious. Other combinations and subcombinationsof features, functions, elements, and/or properties may be claimed inapplications claiming priority from this or a related application. Suchclaims, whether broader, narrower, equal, or different in scope to theoriginal claims, also are regarded as included within the subject matterof the present disclosure.

What is claimed is:
 1. A method of manufacturing a flexible electricalcircuit, comprising: applying an electrically insulating coating to acylinder, wherein the coating is patterned to expose portions of thesurface of the cylinder in a pattern corresponding to an electricalcircuit to be formed; immersing the cylinder at least partially into ametal-containing solution; electrodepositing metal from themetal-containing solution onto the exposed portions of the surface ofthe cylinder; rotating the cylinder until the electrodeposited metalcomes into contact with a flexible substrate contacting a portion of thecylinder; and separating the flexible substrate from the cylinder withthe electrodeposited metal attached to the substrate in the patterncorresponding to the flexible electrical circuit.
 2. The method of claim1, wherein the flexible circuit is a radio frequency identification tag(RFID tag).
 3. The method of claim 1, wherein the flexible substrate isa flexible polymer sheet.
 4. The method of claim 1, further comprisingpatterning the electrically insulating coating with a laser, afterapplying the electrically insulating coating to the cylinder.
 5. Themethod of claim 1, wherein the electrically insulating coating is formedfrom a synthetic fluoropolymer.
 6. The method of claim 1, furthercomprising applying a release layer to the exposed portions of thesurface of the cylinder.
 7. The method of claim 1, further comprisingcompressing the flexible substrate against the cylinder to increaseadhesion between the flexible substrate and the electrodeposited metal,before separating the flexible substrate from the cylinder.
 8. A methodof manufacturing a flexible electrical circuit, comprising: immersing acylinder at least partially into a metal-containing solution, whereinthe cylinder is electrically conductive and includes an electricallyinsulating coating adhered to the outer surface, and wherein the coatingis patterned to expose portions of the outer surface in a patterncorresponding to an electrical circuit to be formed; electrodepositingmetal from the metal-containing solution onto the exposed portions ofthe outer surface of the cylinder; rotating the cylinder until theelectrodeposited metal comes into contact with a flexible substratewrapped around a portion of the cylinder; and separating the flexiblesubstrate from the cylinder with the electrodeposited metal attached tothe flexible substrate in the pattern corresponding to the electricalcircuit.
 9. The method of claim 8, wherein the electrical circuit to beformed is a flexible circuit.
 10. The method of claim 9, wherein thepattern corresponds to a radio frequency identification tag (RFID tag).11. The method of claim 8, wherein the flexible substrate is a flexiblepolymer sheet.
 12. The method of claim 8, wherein the electricallyinsulating coating is formed from a synthetic fluoropolymer.
 13. Themethod of claim 12, wherein the synthetic fluoropolymer coating isformed from a material chosen from the set consisting ofpolytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluorinatedethylene propylene (FEP) and a parylene polymer.
 14. The method of claim8, further comprising applying a release layer to the exposed portionsof the surface of the cylinder, prior to immersing the cylinder at leastpartially into the metal-containing solution.
 15. A method ofmanufacturing a flexible electrical circuit, comprising: providing anelectrically conductive cylinder having an electrically insulatingcoating applied over the outer surface, wherein the coating is patternedto expose portions of the outer surface in a pattern corresponding to aflexible electrical circuit to be formed; immersing the cylinder atleast partially into a metal-containing solution; electrodepositingmetal from the metal-containing solution onto the exposed portions ofthe outer surface of the cylinder; rotating the cylinder until theelectrodeposited metal comes into contact with a flexible substrate; andseparating the flexible substrate from the cylinder with theelectrodeposited metal attached to the substrate in the patterncorresponding to the flexible electrical circuit.
 16. The method ofclaim 15, further comprising patterning the electrically insulatingcoating with a laser to expose portions of the outer surface in thepattern corresponding to the flexible electrical circuit to be formed,prior to immersing the cylinder at least partially into themetal-containing solution.
 17. The method of claim 15, furthercomprising compressing the flexible substrate against the cylinder toincrease adhesion between the flexible substrate and theelectrodeposited metal, before separating the flexible substrate fromthe cylinder.
 18. The method of claim 15, wherein the flexible substrateis a flexible polymer sheet including a heat activated adhesive disposedon one side, and further comprising heating the flexible polymer sheetto activate the adhesive and increase adhesion between the flexiblepolymer sheet and the electrodeposited metal, before separating theflexible polymer sheet from the cylinder.
 19. The method of claim 18,further comprising cooling the flexible polymer sheet to reduce adhesionof the flexible polymer sheet to the cylinder, before separating theflexible polymer sheet from the cylinder.
 20. The method of claim 15,wherein the pattern corresponds to a radio frequency identification tag(RFID tag).